Former Elmo puppeteer and Sesame Street star says latest claims are also without merit; accuser is also writing a book about his alleged experience with Clash.

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This Jan. 24, 2011 photo shows "Sesame Street" muppet Elmo and puppeteer Kevin Clash during the 2011 Sundance Film Festival to promote the film "Being Elmo."

Updated at 11:37 PM PDT on Monday, Nov 26, 2012

The news isn't getting any better for Kevin Clash.

A third man has come forward claiming that he was only 16 when he engaged in a sexual relationship with the former "Sesame Street" star. Clash, 52, who pulled Elmo's strings and voiced the beloved puppet for nearly 30 years before resigning this month, again denies the allegations, as he has denied the similar claims of two other men.

The latest accuser's lawyer, Jeff Herman, confirms to E! News that they will be filing a lawsuit tomorrow in federal court in New York. A press conference is also planned for 1 p.m. ET.

His client has also been writing a book about his liaison with Clash and excerpts will be released tomorrow, as well, Herman says.

"Mr. Clash believes this suit has no merit," a rep for the embattled TV star tells E! News.

Per the New York Daily News, the lawsuit will claim that the plaintiff, who will be suing as John Doe, was 16 when he met Clash on a gay chat line 13 years ago. After a couple of days of chatting, the accuser says he went to Clash's apartment and they engaged in some "sexual activity," Herman told the paper. His client and Clash met up at times in 2003 and 2004, as well, he said.

Clash was also sued for engaging in sexual activity with minor last week by Cecil Singleton, who claims he was 15 when he had inappropriate contact with the children's television star. He clarified in a subsequent press conference that although the two engaged in sexual activity, they did not have sex until Singleton was of legal age.

Singleton was the second accuser to come forward. After coming forward and prompting what was at first Clash's leave of absence from "Sesame Street," his first accuser recanted his allegations, saying any sex that went on occurred consensually when he was an adult.